The project is a study of regulation of transcription during development of the brine shrimp, Artemia. In this biological system, major quantitative changes in rates of RNA synthesis in vivo are paralleled by changes in amounts of RNA polymerases. The principal objectives of the project are the following: (1) define the mechanisms involved in regulating levels of RNA polymerase activity and number of enzyme molecules; (2) identify proteins that are synthesized in a stage-specific manner; (3) isolate specific genes for studies of transcriptional regulation in vitro. These objectives will be pursued by: (1) measuring synthesis and turnover of RNA polymerases by in vivo radiolabeling; (2) examining defined subcellular fractions for appearance of proteins at specific stages; (3) screening a library of cloned DNA sequences to isolate recombinants carrying specific genes.